The invention concerns spinal osteosynthesis systems.
An osteosynthesis system comprising a pedicle screw with two branches which can receive a connecting rod between them is known from document WO 92/03100, FIG. 6. A cylindrical cap has, on its inner face, a thread which can cooperate with a thread on an outer cylindrical face of the branches for the purpose of screwing the cap onto these. A lock mounted movably in rotation on the cap can clamp the rod between the branches when the cap is screwed onto them.
An object of the invention is to make available a system of a type different than that disclosed in said document, and in particular one which allows the lock and the collar to be joined together simply and quickly.
To achieve this object, the invention provides a spinal osteosynthesis system including a rod, a vertebral member comprising two branches which can receive the rod between them, a collar which can prevent the branches from being spaced apart, and a lock which can clamp the rod and can be mounted movably in rotation on the collar, and in which either one of the collar or the lock has a groove which can receive the other of the collar or the lock for mounting the lock on the collar.
Thus, the parts are joined together using a reduced number of components, which simplifies and accelerates assembly. Moreover, the attachment of the two parts is robust and secure.
Advantageously, the collar and the lock have introduction threads for introducing the other of the collar or the lock into the groove.
Advantageously, the collar and/or the lock is elastically deformable for introducing the other of the collar or the lock into the groove.
Thus,it is very easy to join the lock and the collar together to obtain the abovementioned joining, and yet without damaging the quality and stability of the connection obtained.
Advantageously, the lock comprises at least one slot at the level of the groove.
Advantageously, a first of the collar or the lock, preferably the lock, has a tightening thread which can cooperate with a tightening thread of the branches, the second of the collar or the lock extending opposite the tightening thread of the first.
Thus, the second maintains the branches in a position exactly opposite the thread. Any spacing-apart or closing-together of the branches is therefore excluded, irrespective of the stresses tending locally to displace the branches.
Advantageously, the tightening thread of the first is one of the introduction threads.
Thus, it is possible to avoid using numerous threads. Consequently, it is possible to increase the dimensions of the thread and thereby facilitate its production without increasing the dimensions of the component by comparison.
Advantageously, the system is configured in such a way that the tightening thread extends between the groove and the rod.
Advantageously, the system is configured in such a way that the groove extends between the rod and the tightening thread.
Advantageously, the collar comprises an arm which can extend between the branches parallel to the rod and can participate in the mounting of the lock on the collar via the groove.
Advantageously, the arm comprises two parts which can extend on either side of the lock.
Advantageously, the two parts are spaced apart from each other.
Advantageously, at least one of the two parts comprises a slot.
Advantageously, the two parts are elastically deformable.
Advantageously, the two parts are connected to each other.
The invention also provides a combination of a collar and of a lock for an osteosynthesis system according to the invention, the collar comprising a flange, the lock being able to be mounted movably in rotation on the collar, and in which either one of the collar or the lock has a groove which can receive the other of the collar or the lock for mounting the lock on the collar, the collar and the lock having means of assembly for introducing the other of the collar or the lock into the groove.
Other characteristics and advantages of the invention will become clear from the following description of six preferred embodiments which are given as nonlimiting examples.